Human cytomegalovirus (CMV) is the major infectious cause of birth defects in the United States. Recent demonstration that the glycoprotein B (gB)/MF59 vaccine has 50% efficacy in protecting women against primary CMV infection is a landmark in CMV vaccine research. However, 50% efficacy may be insufficient for vaccine licensure. Thus, the challenge is to determine what can be added to a gB-based vaccine to increase efficacy to an acceptable level. Recent work from the PI's laboratory showed that CMV seropositive people have high levels of antibodies that neutralize viral entry into epithelial cells and that comparable levels are not achieved by the gB/MF59 vaccine. Epithelial entry-specific neutralizing epitopes reside within a virion glycoprotein complex consisting of gH, gL, UL128, UL130, and UL131 (gH/gL/UL128-131). The investigator's laboratory recently identified two peptide epitopes, one from UL130 and one from UL131, that are capable of eliciting potent epithelial entry-specific neutralizing responses. The co-PI has developed a novel platform for eliciting antibody responses to peptide epitopes. The desired peptides are engineered into an external loop of the hepatitis virus B core antigen (HBcAg) protein. The modified proteins self- assemble into virus-like particles (VLPs), which serve as potent immunogens and elicit strong antibody responses to the inserted peptide epitopes. We propose to engineer chimeric HBcAg proteins that contain the UL130 and UL131 peptide epitopes and evaluate the chimeric VLPs for their ability to elicit epithelial entry- specific neutralizing activities in mice. Optimal chimeric VLPs will be further evaluated for compatibility with the gB subunit vaccine. The results of the proposed studies may provide a novel vaccine strategy for advancement to clinical development. PUBLIC HEALTH RELEVANCE: Human cytomegalovirus is the major infectious cause of birth defects in the United States. We recently found that two peptide epitopes elicit high levels of antibodies that block viral entry into epithelial cells. Based on these results, a new vaccine strategy of expressing these peptides in the context of the hepatitis B virus core protein will be investigated. The results of the proposed studies may provide a novel vaccine strategy for advancement to clinical development.